APPLICATION OF ADJOINT CMAQ CHEMICAL TRANSPORT MODEL IN THE ATHENS GREATER AREA: SENSITIVITIES STUDY ON OZONE CONCENTRATIONS

An operational meteorology and air quality forecasting system is currently under development by the Environmental Research Laboratory of NCSR “Demokritos”. The system is based on the meteorological model MM5, the in-house EMISLAB emissions processing system and the chemical transport model CMAQ. It is configured to apply on the Greater Athens Area with a 4-domains nested configuration focusing on a high spatial resolution (1x1 km2) inner domain. The system produces meteorological and air quality predictions for a 72-hours time horizon with 1 hour time step. This paper uses the output of the operational system to apply the CMAQ adjoint for ozone sensitivity calculations, focusing for the two days of 18 and 19 July 2005. In the current study, the calculated ground level ozone concentrations at certain defined locations and times are considered as the “response functional”. Sensitivities of the response functional with respect to the state variables (species concentrations on the grid points and species emissions, e.g., NOX, CO, VOCs) are calculated by running the adjoint model backwards in time (reverse mode). The distribution of the sensitivities in the computational domain, obtained for different times, provides essential information for the analysis: isosurfaces of sensitivities delineate influence regions, i.e., areas where perturbations in some concentrations will result in significant changes in the ozone concentrations in the area of interest at the final time